bugfix(filesystem): Tentatively fix hang in file exist cache

[xezon]

This change tentatively fixes a hang in the file exist cache. It was observed when loading a map with a VS2022 build.

The logic was stuck in an infinite hash map lookup.

The theory is that 2 threads modified the FileSystem::m_fileExist map at the same time and corrupted its state.

The callstack indicates that the texture loader thread was perhaps involved, which is one of the few multi threaded systems in the game process.

Perhaps it is a VS2022 specific issue. VC6 builds use a different hash map implementation.

>	generalszh.exe!rts::string_key_equal<AsciiString>::operator()(const rts::string_key<AsciiString> & a, const rts::string_key<AsciiString> & b) Line 292	C++
 	generalszh.exe!std::_Uhash_compare<rts::string_key<AsciiString>,rts::string_key_hash<AsciiString>,rts::string_key_equal<AsciiString>>::operator()<rts::string_key<AsciiString>,rts::string_key<AsciiString>>(const rts::string_key<AsciiString> & _Keyval1, const rts::string_key<AsciiString> & _Keyval2) Line 150	C++
 	generalszh.exe!std::_Hash<std::_Umap_traits<rts::string_key<AsciiString>,FileSystem::FileExistData,std::_Uhash_compare<rts::string_key<AsciiString>,rts::string_key_hash<AsciiString>,rts::string_key_equal<AsciiString>>,std::allocator<std::pair<rts::string_key<AsciiString> const ,FileSystem::FileExistData>>,0>>::_Find_last<rts::string_key<AsciiString>>(const rts::string_key<AsciiString> & _Keyval, const unsigned int _Hashval) Line 1596	C++
 	generalszh.exe!std::_Hash<std::_Umap_traits<rts::string_key<AsciiString>,FileSystem::FileExistData,std::_Uhash_compare<rts::string_key<AsciiString>,rts::string_key_hash<AsciiString>,rts::string_key_equal<AsciiString>>,std::allocator<std::pair<rts::string_key<AsciiString> const ,FileSystem::FileExistData>>,0>>::_Find<rts::string_key<AsciiString>>(const rts::string_key<AsciiString> & _Keyval, const unsigned int _Hashval) Line 1221	C++
 	generalszh.exe!std::_Hash<std::_Umap_traits<rts::string_key<AsciiString>,FileSystem::FileExistData,std::_Uhash_compare<rts::string_key<AsciiString>,rts::string_key_hash<AsciiString>,rts::string_key_equal<AsciiString>>,std::allocator<std::pair<rts::string_key<AsciiString> const ,FileSystem::FileExistData>>,0>>::find(const rts::string_key<AsciiString> & _Keyval) Line 1232	C++
 	generalszh.exe!FileSystem::doesFileExist(const char * filename, unsigned char instance) Line 230	C++
 	generalszh.exe!GameFileClass::Set_Name(const char * filename) Line 189	C++
 	generalszh.exe!GameFileClass::GameFileClass(const char * filename) Line 82	C++
 	generalszh.exe!W3DFileSystem::Get_File(const char * filename) Line 458	C++
 	generalszh.exe!file_auto_ptr::file_auto_ptr(FileFactoryClass * fac, const char * filename) Line 64	C++
 	generalszh.exe!DDSFileClass::DDSFileClass(const char * name, unsigned int reduction_factor) Line 57	C++
 	generalszh.exe!Get_Texture_Information(const char * filename, unsigned int & reduction, unsigned int & w, unsigned int & h, unsigned int & d, WW3DFormat & format, unsigned int & mip_count, bool compressed) Line 1319	C++
 	generalszh.exe!TextureLoadTaskClass::Begin_Compressed_Load() Line 1413	C++
 	generalszh.exe!TextureLoadTaskClass::Begin_Load() Line 1187	C++
 	generalszh.exe!TextureLoadTaskClass::Finish_Load() Line 1256	C++
 	generalszh.exe!TextureLoader::Request_Foreground_Loading(TextureBaseClass * tc) Line 749	C++
 	generalszh.exe!TextureClass::Init() Line 869	C++
 	generalszh.exe!TextureClass::TextureClass(const char * name, const char * full_path, MipCountType mip_level_count, WW3DFormat texture_format, bool allow_compression, bool allow_reduction) Line 757	C++
 	generalszh.exe!WW3DAssetManager::Get_Texture(const char * filename, MipCountType mip_level_count, WW3DFormat texture_format, bool allow_compression, TextureBaseClass::TexAssetType type, bool allow_reduction) Line 1113	C++
 	generalszh.exe!W3DAssetManager::Get_Texture(const char * filename, MipCountType mip_level_count, WW3DFormat texture_format, bool allow_compression, TextureBaseClass::TexAssetType type, bool allow_reduction) Line 183	C++
 	generalszh.exe!Render2DClass::Set_Texture(const char * filename) Line 134	C++
 	generalszh.exe!W3DDisplay::drawImage(const Image * image, int startX, int startY, int endX, int endY, int color, Display::DrawImageMode mode) Line 2646	C++
 	generalszh.exe!GameWindowManager::winDrawImage(const Image * image, int startX, int startY, int endX, int endY, int color) Line 80	C++
 	generalszh.exe!W3DGameWinDefaultDraw(GameWindow * window, WinInstanceData * instData) Line 331	C++
 	generalszh.exe!GameWindowManager::drawWindow(GameWindow * window) Line 1233	C++
 	generalszh.exe!GameWindowManager::winRepaint() Line 1288	C++
 	generalszh.exe!W3DInGameUI::draw() Line 434	C++
 	generalszh.exe!W3DDisplay::draw() Line 1858	C++
 	generalszh.exe!LoadScreen::update(int percent) Line 168	C++
 	generalszh.exe!MultiPlayerLoadScreen::update(int percent) Line 1473	C++
 	generalszh.exe!GameLogic::updateLoadProgress(int progress) Line 1110	C++
 	generalszh.exe!GameLogic::startNewGame(bool loadingSaveGame) Line 1323	C++
 	generalszh.exe!GameLogic::update() Line 3684	C++
 	generalszh.exe!SubsystemInterface::UPDATE() Line 73	C++
 	generalszh.exe!GameEngine::update() Line 922	C++
 	generalszh.exe!Win32GameEngine::update() Line 90	C++
 	generalszh.exe!GameEngine::execute() Line 985	C++
 	generalszh.exe!GameMain() Line 55	C++
 	generalszh.exe!WinMain(HINSTANCE__ * hInstance, HINSTANCE__ * hPrevInstance, char * lpCmdLine, int nCmdShow) Line 903	C++
 	generalszh.exe!invoke_main() Line 107	C++
 	generalszh.exe!__scrt_common_main_seh() Line 288	C++
 	generalszh.exe!__scrt_common_main() Line 331	C++
 	generalszh.exe!WinMainCRTStartup(void * __formal) Line 17	C++
 	kernel32.dll!74e05d49()	Unknown
 	[Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll]	
 	ntdll.dll!7730d6db()	Unknown
 	ntdll.dll!7730d661()	Unknown

[Skyaero42]

Ok

[xezon]

Added a code comment to describe the bug fix